Natural gas is a clean burning fuel relative to gasoline and diesel with improved emission levels of hydrocarbons, nitrogen oxides (NOx), carbon oxides and particulate matter. Increasing concern over exhaust emissions regulation and fuel efficiency has led to an interest in burning combustible gaseous fuels, such as propane, hydrogen, methanol and natural gas, in internal combustion engines. The interest can be more pronounced in relation to the cost of operation of marine vessels on these alternative fuels. Natural gas in particular offers vessel owners the potential for significant reductions in operating expenses versus traditional diesel fuel.
Systems and procedures have been developed for converting existing diesel engines into engines that can combust and be powered by alternative fuels such as natural gas. Such conversions can include modifying the diesel engines with ignition systems including spark plugs and/or diesel pilot fuel, adding tanks for storing the alternative fuel efficiently, such as storing natural gas cryogenically as liquified natural gas (LNG), and adding other components such as gas handling units (GHUs) for converting the alternative fuel from the storage state to a combustible state that can be burned in the engine, and bunker modules for transferring the alternative fuel from a source to the storage tanks. Properly implemented, converting the diesel engines to burn alternative fuels can reduce fuel costs, reduce harmful emissions in the engine exhaust, extend engine life, and reduce noise output by the engine.
Currently, wide scale adoption of engine conversions to alternative fuels as the primary marine transportation fuel for workboats has been stifled by high capital costs of the vessel modifications required to carry large capacities of the alternative fuels to meet mission and journey requirements. For example, a voyage requiring 51,000 gallons of diesel fuel may require over 85,000 gallons of LNG. Additional impediments to adoption include regulatory, i.e., safety, challenges and bunkering (fueling) logistics associated with vessel line haul and midstreaming (refueling while under way) operations, and the uniqueness of each fleet owner's commercial transportation charters, vessel design, region of operation and other operational factors. The varying requirements for the marine vessels force unique, non-scalable alternative fuel storage and management solutions, resulting in high capital cost of conversion for virtually all conversion projects. The lack of standardization prevents fleet owners from realizing economies of scale, and often times results in decisions to forego conversion to alternative fuels due to prohibitively low returns on investment.